CoAl-LDH Nanosheets Research Articles

Hydroxy salt induced CoAl-LDH nanosheet composite membrane for pervaporation desalination

Pervaporation is a promising desalination technology. Developing high-performance and stable pervaporation membranes with high continuity structure remains a significant challenge. This study reports the development of a novel layered double hydroxide (LDH) nanosheet composite membrane fabricated using a hydroxyl salt induction method. This approach facilitated the in-situ nucleation and growth of the CoAl-LDH nanosheets on polyvinylidene fluoride (PVDF) substrate, reducing precursor concentration and enhancing preparation efficiency. The resulting cross-compatible architecture closely integrated the dense LDH nanosheet separation layer with the flexible PVDF support. The microstructure and morphology of the hydroxyl salt layer and its transformed CoAl-LDH composite membrane were comprehensively investigated. The optimized membrane was applied for pervaporation desalination (3 wt% NaCl, 50 °C), achieving a high flux of 38.4 kg·m−2·h−1 and exceptional NaCl rejection of 99.9 %. It also demonstrated excellent tolerance to a wide salinity range, maintaining 99.6–99.9 % rejection even at 20 wt% NaCl, while the flux remained stable at 26.7 kg·m−2·h−1. Long-term testing confirmed the consistent separation performance and operational stability, underscoring the great potential of this advanced membrane material for practical pervaporation desalination applications.

Stepwise Construction of MoS2@CoAl-LDH/NF 3D Core-Shell Nanoarrays with High Hole Mobility for High-Performance Asymmetric Supercapacitors.

Supercapacitors (SCs) have received widespread attention as excellent energy storage devices, and the design of multicomponent electrode materials and the construction of ingenious structures are the keys to enhancing the performance of SCs. In this paper, MoS2 nanorods were used as the carrier structure to induce the anchoring of CoAl-LDH nanosheets and grow on the surface of nickel foam (NF) in situ, thus obtaining a uniformly distributed MoS2 nanorod@CoAl-LDH nanosheet core-shell nanoarray material (MoS2@CoAl-LDH/NF). On the one hand, the nanorod-structured MoS2 as the core provides high conductivity and support, accelerates electron transfer, and avoids agglomeration of CoAl-LDH nanosheets. On the other hand, CoAl-LDH nanosheet arrays have abundant interfacially active sites, which accelerate the electrolyte penetration and enhance the electrochemical activity. The synergistic effect of the two components and the unique core-shell nanostructure give MoS2@CoAl-LDH/NF a high capacity (14,888.8 mF cm-2 at 2 mA cm-2) and long-term cycling performance (104.4% retention after 5000 charge/discharge cycles). The integrated MoS2@CoAl-LDH/NF//AC device boasts a voltage range spanning from 0 to 1.5 V, achieving a peak energy density of 0.19 mW h cm-2 at 1.5 mW cm-2. Impressively, it maintains a capacitance retention rate of 84.6% after enduring 10,000 cycles, demonstrating exceptional durability and stability.

High-Performance Catalytic Reduction of 4-Nitrophenol to 4-Aminophenol over Pt Nanoparticles Supported on Co-Al LDH Nanosheets

In this study, a Pt@Co-Al LDH hybrid structure was fabricated by assembling the metal precursor PtCl62− with the exfoliated LDH nanosheets followed by in situ reduction by NaBH4. The morphology, composition and microstructure of the hybrid were characterized by FESEM, HRTEM, XRD, XPS and BET techniques. Pt nanoparticles (NPs) with an average particle size of 3.1 nm were successfully and uniformly loaded on the surface of LDH nanosheets. The catalytic activity of the Pt@Co-Al LDH hybrid was tested for the reduction of 4-nitrophenol, which is one of the most frequent pollutants in wastewater effluent from the pharmaceutical and textile industries. The hybrid displays superior catalytic activity and stability in the reduction of 4-NP under environmental conditions with NaBH4 as a reducing agent. The hybrid can be recovered in a simple way and still shows high catalytic activity after five reuses.

Monodispersed ZIF-67 in situ nucleated on CoAl-LDH nanosheets for efficient carbamazepine degradation via activation of peroxymonosulfate

Abundant exposed ligand-unsaturated sites of Co have been found to enhance the catalytic oxidation property of ZIF-67 material for peroxymonosulfate (PMS) catalysis. Nevertheless, serious stacking of ZIF-67 still poses a challenge to its application. Herein, we employed a specific in situ growth strategy to establish an LDHNS@ZIF-67 composite based on morphology modulation and performance optimization for carbamazepine (CBZ) degradation. ZIF-67 crystals were successfully grown in situ via nucleating on the CoAl-LDH nanosheets (LDHNSs) substrate surface, which facilitated the crystals’ dispersion. LDHNS@ZIF-67 (0.1 M) was optimized to display outstanding PMS catalytic activity for CBZ degradation, with almost 100% degradation in 5 min (PMS dose, 0.2 mM, catalyst dose, 25 mg/L, and CBZ concentration, 5 ppm). Quenching and electron paramagnetic resonance (EPR) tests confirmed that both radical substances (SO4•-) and nonradical substances (1O2) dominated the reaction system. As the active site, Co(II) ions on the LDHNS@ZIF-67 (0.1 M) surface effectively promoted active substance formation. The intermediate degradation products and pathways for CBZ were investigated. Toxicity assessment for CBZ and its intermediates was conducted. This work will broaden the application of ZIF-67 materials in advanced oxidation process design based on persulfate.

Switchable superlyophobic CoAl-layered double hydroxide (LDH)-based mesh membranes for separation of various oil/water systems and removal of soluble organic pollutants

Switchable surface wettability has attracted tremendous attention owing to its potential applications, but it is still thorny to construct under-liquid dual superlyophobic surfaces for reversible separation of emulsified oil/water mixtures and treatment of complex oily wastewater. In this work, a CoAl-LDH-based mesh membrane was prepared for switchable separation of emulsified oily wastewater. The interpenetrating CoAl-LDH nanosheets were grown on the stainless steel mesh (SSM) forming a micro-/nano hierarchical structure via a hydrothermal method, which endows the membrane with under-liquid dual superlyophobicity. The obtained CoAl-LDH membrane exhibited switchable separation capability for both oil/water mixtures and oil/water emulsions with high fluxes and efficiencies (99.7%). In addition, the CoAl-LDH membrane could not only separate but also photodegrade the oil-in-water (O/W) emulsions containing soluble organic pollutants. Interestingly, after introducing a ZnO nanorod layer, the LDH/ZnO membrane exhibited progressive removal efficiency (99%) and photodegradation efficiency (＞99%) for methylene blue (MB). The cycled and harsh condition tests also confirmed the stability and robustness of the prepared membranes. The excellent separation performance and photocatalytic property endow the membranes appealing to practical oil/water separation and oily wastewater treatment.

CoAl-LDH decorated with cerium oxide as an efficient adsorbent for restoring low-concentration phosphate in wastewater.

The requirement for the removal of phosphorus (P) from wastewater has become progressively stringent, therefore, it is essential to remove low-concentration phosphate from secondary effluents through a tertiary treatment. One of the biggest challenges in removing phosphate from wastewater is the development of low-cost, green, and pollution-free adsorbents. In this study, novel, eco-friendly and low-cost CeO2 nanosphere modifying CoAl-LDH nanosheets (CoAl-LDH/CeO2) were successfully fabricated using a classical hydrothermal strategy. The microstructure and morphology of CoAl LDH/CeO2 were characterized using SEM, TEM, FTIR, XRD, TG, XPS, and BET techniques. The performance of the P adsorption from water for CoAl-LDH/CeO2 was investigated. The influences of adsorption parameters, such as adsorbent dosage, pH, phosphate concentration, adsorption time, and experimental temperature, were investigated through batch adsorption experiments. The batch adsorption experiments showed that the P removal by CoAl-LDH/CeO2 could reach 93.4% at room temperature within 60 minutes. CoAl-LDH/CeO2 showed ultrafast and high-efficiency adsorption for low concentration P contaminated wastewater. Pseudo-second order model exhibited better fitting with the kinetics of the phosphate adsorption, while the Freundlich model well-described the isotherm results (R2 > 0.999). Although Cl-, NO3-and SO42- coexisted in the solution, CoAl-LDH/CeO2 still possessed favourable selectivity for phosphates. More importantly, the adsorption capacities of CoAl-LDH/CeO2 retained over 85% after five cycles. Therefore, the low cost and sustainable utilization of CoAl-LDH/CeO2 for the phosphate removal from secondary effluent with phosphate at a low concentration highlights its potential application to alleviate eutrophication.

Frustrated Lewis pairs on metal-cation vacancy catalysts enhanced the electroreduction of NO to NH3

Metal-cation vacancies in CoAl-LDH nanosheets prepared by simple etching facilitate abundant surface oxygen vacancies. They promote the formation of frustrated Lewis pairs, which enhance the electrocatalytic NO reduction to NH3.

(Invited) Layered Double Hydroxides with Enhanced Interlayer Space for Electrochemical Energy Storage and Deionization

Layered double hydroxides (LDHs) have been extensively studied as promising functional nanomaterials owing to their excellent electrochemical activity and tunable chemical composition. In this work, we presented a series of investigations on enhanced interlayer space of LDHs for electrochemical energy and deionization.Firstly, using acetate anions (Ac-) as an intercalating element, NiCo-LDH nanosheets arraying on Ni Foam with different amounts of Ac- anions intercalation or volumes of hydrothermal solution were prepared by a simple hydrothermal method. The optimized amount of Ac- anions expanded the interlayer space of LDH nanosheets from 0.8 to 0.94 nm. An ultrahigh specific capacity of 1200 C g-1 at 1 A g-1 (690 C g-1 without Ac- anions), outstanding rate capability of 72.5% at 30 A g-1 and cycle stability of 79.90% after 4500 cycles, which were mainly attributed to the higher interlayer spacing of Ac- anions intercalation.Moreover, CoAl-LDH nanosheets intercalated by sodium dodecyl sulfate (SDS) with an enhanced interlayer spacing from 0.76 to 1.33 nm are synthesized and used as an anode of electrosorption. The enlarged interlayer spacing provides an enhanced ion diffusion channel and improves the utilization of the interlayer electroactive sites, while heat treatment transferring LDHs to layered metal oxides offers additional active oxidation reaction sites to facilitate the electro-sorption rate, contributing to the high salt adsorption capacity (31.78 mg g-1) and average salt adsorption rate (3.75 mg g-1 min-1) at 1.2 V in 500 mg L-1 NaCl solution. In addition, the excellent long-term cycling stability (92.9%) after 40 cycles proves the strong electronic interaction between SDS and the host layer, which is validated by density functional theory calculations later on.In addition, ionic surfactants like SDS and cetyl trimethyl ammonium bromide (CTAB) can be used to modify the morphology of LDH. The original LDH shows microspheres formed by nanorods, and LDH-CTAB is similar, yet more tangled, while LDH-SDS is like micro flowers consisting of interwoven nanosheets. LDH-SDS achieved better electrochemical performance (1003.6 C g-1 at 1 A g-1 and 73.84% after 3500 cycles) than LDHs-CTAB (430.54 C g-1, 57.3%), and both higher than the original LDH (278.5 C g-1, 54.3%), while the electrocatalytic performance like Tafel slope follows an opposite trend owing to the difficulty of bubbles detachment from the nanosheets or nanorods, clearly showing the importance of morphology regulation in the synthesis of nanomaterials.

Combining CoAl-LDH nanosheets with Bi19S27Br3 nanorods to construct a Z-scheme heterojunction for enhancing CO2 photoreduction

In this study, a novel Z-scheme Bi19S27Br3/CoAl-LDH heterojunction was prepared. An interface charge transfer channel was established between Bi19S27Br3 and CoAl-LDH, accelerating the transition efficiency of interface electrons from CoAl-LDH to Bi19S27Br3. Thereby ensuring more excited electrons to participate in CO2 photoreduction reactions. The reduction products were tested under artificial light conditions, and triethanolamine was selected as a sacrificial agent. After 5 h of illumination, the CO yield of Bi19S27Br3/CoAl-LDH Z-scheme heterojunction was 86.41 μmol·g−1 is 4 times and 7 times higher than Bi19S27Br3 and CoAl-LDH, respectively. The yield of CH4 in Bi19S27Br3/CoAl-LDH is 3.97 μmol·g−1 is 4 times higher than CoAl-LDH. Also Bi19S27Br3 itself does not produce CH4. The results indicate that the Z-scheme heterojunction effectively enhances the photoreduction ability of CO2, providing a new approach for accurately controlling the direction of photo generated charge separation to prepare high-performance photocatalysts.

Engineering 2D/2D oxygen vacancy-rich CoAl LDH/rGO sheet-on-sheet heterostructures with improved charge storage for supercapacitors

Layered double hydroxides (LDHs) as electrode materials for supercapacitors still suffer from limited actual specific capacities and unsatisfactory cycling performance owing to their poor intrinsic electrical conductivity and insufficient electroactive sites. Herein, oxygen vacancy (Ov)-rich CoAl-LDH nanosheets are attached onto reduced graphene oxide (rGO) nanosheets to form 2D/2D Ov-CoAl-LDH/rGO sheet-on-sheet heterostructures via a facile precipitation-reduction reaction followed by hydrothermal treatment. The introduction of rich Ov defects in CoAl-LDHs enhances the electrical conductivity, while the attachment of Ov-CoAl-LDH nanosheets on the surface of rGO nanosheets not only reduces the aggregation of Ov-CoAl-LDH nanosheets and thus exposes abundant electroactive sites, but also maintains good structural stability. Theory calculations indicate that the Fermi-level difference of two components triggers interfacial charge separation while creating a built-in electric field at the Ov-CoAl-LDH/rGO interface, which favors rapid electron/ion migration and accelerates charge storage kinetics. The optimized Ov-CoAl-LDH/rGO nanocomposites deliver specific capacities of 984 C g−1 at 3 A g−1 and 708 C g−1 at 20 A g−1 and retain an initial capacity of 90 % after 10,000 cycles at 10 A g−1. These findings showcase a feasible strategy to endow 2D/2D LDHs/graphene heterostructures with enhanced charge storage performance.

Engineering oxygen vacancy-rich CoAl layered double hydroxides coupled with N-doped carbon nanotubes as electrodes for supercapacitors

Layered double hydoxides (LDHs) as electrode materials for supercapacitors still suffer from unsatisfactory rate capability owing to their limited electrical conductivity and sluggish ion diffusion kinetics. In this work, a vacancy engineering strategy coupled with a nanocomposite method is proposed to construct oxygen vacancy (Ov)-rich CoAl-LDH nanosheets coupled with N-doped carbon nanotubes (N-CNTs) using a one-step precipitation-reduction reaction. Experimental analyses and theoretical calculation results indicate that the rich Ov defects in CoAl-LDHs not only effectively enhance the electrical conductivity but also reduce the surface adsorption barrier of electrolyte ions, thereby triggering fast charge storage kinetics. In addition, Ov-rich CoAl-LDH nanosheets coupled with N-CNTs are well dispersed, which not only enrich electroactive sites but also further increase the charge transport. Consequently, the obtained N-CNT@Ov-CoAl-LDH nanocomposites demonstrate a specific capacity of 1068 C g−1 at 3 A g−1 and maintain a capacity retention of 78% even at 20 A g−1, together with a capacity retention of 91% after 10,000 cycles at 10 A g−1. This work provides insights for designing and engineering LDHs-based electrodes with improved charge storage performance through coupling the vacancy engineering with the nanocomposite method.

Dynamic Morphological Evolution of Co-Based Layered Double Hydroxide Nanosheets Investigated by In Situ Electrochemical-Atomic Force Microscopy

With excellent electrochemical activity, low consumption, and easy synthesis, Co-based layered double hydroxides (LDHs) have been applied to electrochemical energy conversion and storage devices. Understanding the mechanisms of morphological evolution and capacity changes under potential cycles is critical for the design of high-performance materials of Co-based LDHs. Here, we monitored the morphological evolution of two kinds of CoFe-LDH nanosheets and four kinds of CoAl-LDH nanosheets using in situ electrochemical-atomic force microscopy. The CoFe-LDH nanosheets present the growth of granular particles and the deterioration of capacity performances, which might be due to the irreversible conversion of hydroxide into oxyhydroxide under potential cycles. The CoAl-LDH nanosheets maintain more capacity and do not form granular particles under potential cycles, resulting from the electrochemical reaction reversibility of Co2+ and the stability of the host hydroxide layer enhanced by Al3+. The introduction of Al3+ into the Co-based LDH structure is conducive to cyclic stability of capacity compared to that of Fe3+. Additionally, the CoAl-LDH nanosheets with different Co/Al molar ratios present varying degrees of dissolution and variations of capacity under potential cycles. A moderate Co/Al molar ratio of CoAl-LDH nanosheets is beneficial to cyclic stability. These findings would provide a deep insight into the mechanisms of capacity changes based on in situ morphological evolution and support for the optimization of such material performance.

Facile fabrication of CoAl-LDH nanosheets for efficient rhodamine B degradation via peroxymonosulfate activation.

Layered double hydroxides (LDHs) have been extensively investigated as promising peroxymonosulfate (PMS) activators for the degradation of organic pollutants. However, bulk LDHs synthesized using conventional methods possess a closely stacked layered structure, which seriously blocks active sites and yields low intrinsic activity. In this study, we exfoliated bulk CoAl-LDHs to fabricate CoAl-LDH nanosheets by alkali-etching and Ostwald ripening via a simple hydrothermal process in a KOH solution. The exfoliated LDHs possessed the typical nanosheet structure with more exposed active sites for PMS activation, and hence, boosted the degradation of the pollutants. CoAl-1 exhibited an outstanding catalytic performance as the PMS activator for rhodamine B (RhB) degradation with the apparent rate constant of 0.1687 min-1, which was about 3.63 and 5.02 times higher than that of commercial nano-Co3O4 and bulk CoAl-LDH, respectively. The maximum RhB degradation of 93.1% was achieved at the optimal reaction conditions: catalyst dose 0.1 g L-1, PMS concentration 0.3 mM, pH 7, and temperature 298 K. Further analysis of RhB degradation mechanism illustrated that singlet oxygen (1O2) dominated RhB degradation in the CoAl-1/PMS system, while ˙OH, ˙O2-, and ˙SO4- may mainly serve as the intermediates for the generation of 1O2 and were indirectly involved in the degradation. This study provides a promising strategy for developing two-dimensional LDH nanosheets for wastewater remediation.

Self-assembled Co-Al LDH and TiO2 nanocomposites as a novel electrode for supercapacitors

A novel Co-Al layered double hydroxide/titanium dioxide (Co-Al LDH/TiO2) nanocomposite is fabricated by the electrostatic assembly of Co-Al LDH and TiO2 nanosheets from exfoliation. The layer-by-layer nanocomposite structure effectively improves the electrochemical performance by providing abundant utilization of active sites and facilitating rapid ionic/electronic transport. The Co-Al LDH/TiO2 electrode exhibits an enhanced specific capacitance of 611.4 F g−1 at a current density of 10 mA cm−2 and good cyclic stability (81.4% capacity retention after 2000 cycles) compared with Co-Al LDH. A solid-state asymmetric supercapacitor is prepared from the Co-Al LDH/TiO2 as positive electrode and active carbon as negative electrode. The Co-Al LDH/TiO2//AC retains 92.7% initial capacitance and 94.1% coulombic efficiency after 2000 cycles at 20 mA cm−2. The Co-Al LDH/TiO2 nanocomposite is a promising electrode material for the supercapacitors.

Ultra-thin CoAl layered double hydroxide nanosheets for the construction of highly sensitive and selective QCM humidity sensor

To achieve real-time monitoring of humidity in various applications, we prepared facile and ultra-thin CoAl layered double hydroxide (CoAl LDH) nanosheets to engineer quartz crystal microbalances (QCM). The characteristics of CoAl LDH were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), Brunauer–Emmett–Telle (BET), atomic force microscopy (AFM) and zeta potential. Due to their large specific surface area and abundant hydroxyl groups, CoAl LDH nanosheets exhibit good humidity sensing performance. In a range of 11.3% and 97.6% relative humidity (RH), the sensor behaved an ultrahigh sensitivity (127.8 Hz/%RH), fast response (9.1 s) and recovery time (3.1 s), low hysteresis (3.1%RH), good linearity (R2 = 0.9993), stability and selectivity. Besides, the sensor can recover the initial response frequency after being wetted by deionized water, revealing superior self-recovery ability under high humidity. Based on in-situ Fourier transform infrared spectroscopy (FT-IR), the adsorption mechanism of CoAl LDH toward water molecules was explored. The QCM sensor can distinguish different respiratory states of people and wetting degree of fingers, as well as monitor the humidity in vegetable packaging, suggesting excellent properties and a promising application in humidity sensing.

Antifungal CoAl layered double hydroxide ultrathin nanosheets loaded with oregano essential oil for cereal preservation

Fungal infestation of cereals seriously affects human health and the economy. Protecting cereals from fungal infestation is meaningful. Therefore, safe and economical antifungal agents must be explored. Oregano essential oil (OEO) has broad-spectrum antifungal activity but is unstable and poorly water-dispersible. CoAl-LDH ultrathin nanosheets (CoAl-LDH UNs) are a biosafe carrier with peroxidase-like activity and good water dispersibility. A new nanocomposite was constructed by integrating OEO and CoAl-LDH UNs named OEO/CoAl-LDH UNs. The antifungal activity of OEO was improved for the synergetic effect of OEO and CoAl-LDH UNs. OEO/CoAl-LDH UNs showed excellent antifungal activity against Fusarium moniliforme, Fusarium graminearum and Aspergillus flavus. A polyvinyl alcohol film containing OEO/CoAl-LDH UNs was prepared as a food package and effectively inhibited fungal infestation on cereals. This work can provide some insights for the exploration of other new antifungal materials. The good biosafety of this antifungal material can be effectively applied to food packaging.

ZIF-67 dodecahedron coupled with CoAl-layered double hydroxide as S-scheme heterojunction for efficient visible-light-driven hydrogen evolution

Photocatalytic hydrogen generation is a potential strategy to solve the problem of energy shortage and environmental pollution. In this study, we adopted a novel in-situ growth scheme to construct the ZIF-67@CoAl LDH S-scheme heterojunction composite photocatalyst based on morphology modulation and energy band structure design. The outstanding catalytic performance of the composite photocatalyst can be ascribed to the following aspects: 1) the large specific surface area of ZIF-67 dodecahedron could provide abundant active sites; 2) the serious aggregation of CoAl LDH nanosheets were efficiently broken; 3) the light absorption of the composite catalyst were improved; 4) the recombination of photogenerated electrons and holes is effectively inhibited by the architecture of S-scheme, that abound electrons could involve in hydrogen evolution reactions. Thus, the hydrogen production of ZIF-67@CoAl LDH could reach 606.26 µmol h−1 g−1, which equal to 8.4 and 26.1 times that of pristine ZIF-67 and pure CoAl LDH. This work will provide a new insight in the construction of heterojunction photocatalysts.

Facile fabrication of ultrafine CoNi alloy nanoparticles supported on hexagonal N-doped carbon/Al2O3 nanosheets for efficient protein adsorption and catalysis

C–CoNi/@Al2O3 nanosheets were well constructed with CoAl-LDH nanosheets as a precursor, and exhibited excellent performance as both a catalyst and an adsorbent.

High performance flexible asymmetric supercapacitor constructed by cobalt aluminum layered double hydroxide @ nickel cobalt layered double hydroxide heterostructure grown in-situ on carbon cloth

HypothesisThree-dimensional layered layered double hydroxide (LDH) nanostructure materials grow in-situ on excellent conductive and flexible carbon cloth (CC) substrate not only reduce the ability of binders in resisting ions transfer, but also make them to be quasi-vertically arranged well on substrates without aggregation. This would result in enough electroactive sites, to obtain superior electrochemical performance. ExperimentsA hierarchical CoAl-LDH@NiCo-LDH composite was prepared on a surface-modified carbon cloth by a simple two-step hydrothermal process. In this process, CoAl-LDH nanosheets (NSs)/CC acting as the inner core were wrapped up in NiCo-LDH nanoneedle arrays (NNAs) evenly. Also, a flexible quasi-solid-state supercapacitor device was constructed using CoAl-LDH@NiCo-LDH/CC and activated carbon (AC) as a positive electrode and a negative electrode, respectively. FindingsThe CoAl-LDH@NiCo-LDH/CC developed had an excellent specific capacitance (2633.6F/g at 1 A/g) with remarkable cyclic performance (92.5% retention of its incipient over 5000 cycles at 4 A/g). The flexible quasi-solid-state supercapacitor device CoAl-LDH@NiCo-LDH/CC//AC/CC yielded a splendid energy density of 57.8 Wh/kg at a power density of 0.81 kW/kg and a brilliant power density of 16.09 kW/kg at 38.0 Wh/kg in a broad potential window of 1.55 V. Furthermore, the exceptional cyclic stability and excellent flexibility of the device show it can be applied in flexible energy storage systems.

Heterostructure of ultrafine FeOOH nanodots supported on CoAl-layered double hydroxide nanosheets as highly efficient electrocatalyst for water oxidation

The supported and dispersed ultrafine active species for electrocatalytic water oxidation are quite promising for the high intrinsic activity. A novel heterostructure of ultrafine FeOOH nanodots with an average size of 2.3 nm supported on CoAl-LDH nanosheets, is constructed by a facile method under ambient conditions. The as-prepared FeOOH@CoAl-LDH shows a strong interfacial interaction upon the formation of heterostructure, and is demonstrated as a highly efficient and stable electrocatalyst that demands 272 mV to attain 50 mA cm−2 and exhibits a Tafel slope of 40 mV dec−1. Moreover, density functional theory calculations manifest the coupling of FeOOH with CoAl-LDH can effectively decrease the energy barrier during the water oxidation process by optimizing the adsorption free energy of intermediates in the reaction pathway. The successful development of FeOOH@CoAl-LDH can shed light on the design of novel electrocatalysts that can fully take advantages of small size, heterostructure and synergistic effect.